Rabiaa Haouala

Variation in chemical composition and allelopathic potential of mixoploid Trigonella foenum-graecum L. with developmental stages

This study was conducted to evaluate the influence of developmental stages (vegetative, flowering and fruiting) of mixoploid fenugreek aerial parts on their chemical composition and allelopathic potential, assessed on lettuce germination and seedling growth. Aqueous and organic extracts significantly delayed germination, reduced its rate and affected seedling growth. Ethyl acetate and methanol extracts of aerial parts harvested at vegetative stage were the most toxic for lettuce germination and seedling growth, respectively. LC-MS/MS analysis of T. foenum-graecum aerial parts methanolic extract showed nine different flavonol glycosides (quercetin and kaempferol glucosides). Chemical composition of aerial parts differed with the developmental stage; indeed, at the vegetative and fruiting stages, analysis revealed the presence of 9 compounds as compared to only 6 compounds at the flowering stage. Thus, it is necessary to follow the qualitative changes of allelochemicals production at different developmental stages to identify the most productive one.

Effect of the Extracts of the Spiderflower, Cleome arabica, on Feeding and Survival of Larvae of the Cotton Leafworm, Spodoptera littoralis

Abstract Aqueous and organic (hexane, chloroform, and methanol) extracts of siliquae, stems and leaves, and seeds of Cleome arabica L. (Brassicales: Capparidaceae) were evaluated in the laboratory for their antifeeding and insecticidal effect on larvae of the cotton leafworm, Spodoptera littoralis (Boisduval) (Lepidoptera, Noctuidae), using a leaf dipping bioassay with castor bean, Ricinus communis L. (Malpighiales: Euphorbiaceae), leaf discs. The polar extracts caused significant mortality. At the highest dose, C. arabica extracts exhibited significant antifeeding and phagostimulating activities against S. littoralis larvae. Under no-choice conditions, the methanol extract of siliquae was the most active, and the antifeedant index calculated over 24 hr for 3rd instar larvae varied significantly from 16 to 37%. Using nutritional indices, it was established that there was a significant decrease in growth rate concomitant with a reduction in consumption. These results suggest the presence of anti-feeding and/or toxic substances in the extracts that may be useful in developing bio-insecticides based on C. arabica extracts for use in integrated pest management of leafworm and other agricultural pests.

Phytotoxic activity and chemical composition of Cassia absus seeds and aerial parts

Abstract The present study was conducted to assess the phytotoxic potential and the phytochemical composition of Cassia absus. Aqueous extracts caused significant reduction in root growth of Lactuca sativa. Seed extract was more effective than aerial part extract. Successive extractions of this plant were performed using solvents with increasing polarities. The methanolic seed extract exerted strong phytotoxic effect on seedling growth, followed by petroleum ether extract of the aerial part. The phytochemical investigation showed that among the organic extracts, methanol extracts of seeds and aerial parts contained the highest amounts of total phenolics and proanthocyanidins. Seeds were rich in linoleic acid followed by palmitic acids. Palmitic, stearic and arachidic acids were the major fatty acids in aerial parts. HPLC-DAD analysis of the methanolic extracts revealed the presence of luteolin in C. absus aerial parts.

Antifungal activity of aqueous and organic extracts from Withania somnifera L. against Fusarium oxysporum f. sp. radicis-lycopersici

The aim of this study was to evaluate the in vitro antifungal activity of aqueous and organic extracts from native Withania somnifera L. leaves, stems, and fruits against Fusarium oxysporum f. sp. radicis-lycopersici (FORL), the causal agent of Fusarium Crown and Root Rot disease in tomato. Aqueous and organic extracts (used at 1, 2, 3 and 4%) were added to molten Potato Dextrose Agar (PDA) medium. After pathogen challenge, cultures were incubated at 25°C for 5 days. All extracts tested, whatever the concentrations used, showed a strong antifungal activity toward targeted pathogen. FORL response to the different extracts assessed using the poisoned food technique, varied depending on plant organs, concentrations tested and organic solvent used for extraction. For aqueous extracts, fruit extract used at 2% exhibited the highest antifungal potential where FORL growth was decreased by 56.27%, relative to the untreated control, compared to 52 and 45.34% achieved using stem and leaf extracts at 3%, respectively. The highest antifungal activity of organic extracts was registred at the highest concentration used (4%). FORL was found to be more sensitive to fruit extracts than those from leaves and stems. Among the three organic extracts tested, butanolic fractions were the most active against FORL growth. The highest antifungal potential expressed by 62.03% decrease in pathogen radial growth was displayed by butanolic stem extracts applied at 4%. These results indicate that native W. somnifera plants may be exploited as potential source of allelochemicals biologically active against FORL.

Effects of moderate static magnetic field presowing treatment on seedling growth and oxidative status in two Raphanus sativus L. varieties

Improvement of seed performance by static magnetic field (SMF) constitutes a safe ecological way to substitute chemicals use. In laboratory conditions, we studied the effects of presowing seeds of two varieties of Raphanus sativus (Red: R.R, Red and White: R+W) by moderate SMF on seedlings’ growth and oxidative status and this by using different intensities (100 and 200 mT) and exposure times (2 and 3 h). For radish, the SMF pretreatment of 100 mT/3 h induced significant enhancement of 8 day-old seedling biomass production and this by about 26 and 29% for respectively the RR and the R+W varieties. However, R.R seems to be more sensitive to SMF than R+W based on biomass production. Moreover, for the beneficial pretreatment of 100 mT/3 h, SMF-induced effects were also observed when white light was substituted by blue one using light filters. Besides, catalase (CAT) activity was significantly stimulated in radish plantlets (about 36% in cotyledons). Nevertheless, assimilatory pigments decreased (p<0.05) significantly (by about an average of 25%) but malondialdehyde (MDA) content remained unvaried. To conclude, SMF-presowing -at the treatment of 100 mT/3 h- allowed, in our experimental conditions, the improvement of R. sativus initial growth while keeping a good oxidative status. Keywords : Performance, presowing, radish, static magnetic field African Journal of Biotechnology Vol. 12(3), pp. 275-283

In vitro regeneration of the medicinal plant Cassia absus L.

Summary Cassia absus L. is a medicinal plant with commercial value. In order to establish a protocol for its regeneration from nodal explants, C. absus was proliferated in vitro using 1.0_ Murashige and Skoog (MS) medium containing 3% (w/v) sucrose, 0.8% (w/v) agar, 0.05% (w/v) charcoal, and different concentrations of 6-benzylaminopurine (BAP), kinetin, zeatin, or isopentenyl adenine (2iP) under controlled temperature, humidity, and light conditions. Shoot induction was achieved at various rates on all media tested. MS medium containing 0.5 mg l-1 BAP gave the optimum results for shoot initiation and proliferation, with an average shoot length of 12.4 mm and an average of 2.7 leaves per shoot.The effect of 0.5 mg l-1 BAP combined with 0.1 mg l-1 gibberellic acid (GA3) was also tested under the same conditions to improve growth and increase shoot length. Shoots induced on this medium were significantly longer (13.4 mm) with more leaves (3.3 per shoot) than on 1.0_ MS medium containing 0.5 mg l-1 BAP alone. Explants with developed micro-shoots were transferred to 1.0_ MS multiplication medium supplemented with 0.1 mg l-1 GA3 plus different concentrations and combinations of BAP and an auxin [1-naphthaleneacetic acid (NAA) or indole 3-butyric acid (IBA)] for shoot multiplication and elongation. The maximum average of shoot length (35.0 mm) and the highest shoot elongation rate (SER = 2.4 mm shoot-1 week-1) were recorded on 1.0_ MS medium containing 0.5 mg l-1 BAP, 0.1 mg l-1 NAA, and 0.1 mg l-1 GA3. The elongated micro-shoots were excised and transferred onto to 1.0_ or 0.5_ MS medium supplemented with different concentrations of IBA or NAA for root induction. Shoots grown on 0.5_ MS medium with 2 mg l-1 IBA gave the maximum rooting percentage (93.8%) compared to those on 1.0_ MS medium (25%). A protocol for direct shoot induction has been established, however further research must be undertaken to increase the rate of shoot multiplication to produce viable plants.

A NEW DAMMARANE TRITERPENE FROM Cleome arabica

A new dammarane triterpene was isolated from the seed extracts of Cleome arabica L. found growing in Tunisia. The structure of this novel phytoconstituent was elucidated by extensive spectroscopic techniques, including UV, IR, 1D, and 2D NMR and ESI-MS and HR-ESI-MS experiments.

Biochemical composition of Tunisian Nigella sativa L. at different growth stages and assessment of the phytotoxic potential of its organic fractions

Abstract The present study was conducted to study some biochemical characteristics of Tunisian Nigella sativa at different developmental stages of plant growth (vegetative, flowering and fruiting stages) and to screen the chemical constituents and the phytotoxic activity of their organic extracts on lettuce (Lactuca sativa L.). The GC–MS analysis of petroleum ether fractions revealed that N. sativa seeds were rich in linoleic acid (58% of total fatty acids), oleic acid (22% of total fatty acids) and palmitic acid (12% of total fatty acids). The fatty acid composition of aerial parts showed an increase in the level of saturated fatty acids accompanied by a concomitant decrease of polyunsaturated fatty acids levels during the developmental stage. The phytochemical investigation showed that among the organic extracts, the methanolic extract from aerial parts harvested at the fruiting stage contained the highest amounts of phenolic and flavonoid compounds. The phytotoxic study revealed that N. sativa negatively affected the growth of lettuce plants. This effect was largely dependent on the developmental stage at which material was collected and the nature of extracting solvent. The methanolic extract of aerial parts harvested at the vegetative stage was the most active on seedling growth of lettuce.

Stimulatory effect on pea of Typha Angustifolia L. extracts and their chemical composition

ABSTRACT In this study, the influence of aqueous and organic extracts of different plant parts (flowers, leaves, and stems) of Typha angustifolia on the germination and early seedling growth of field pea (Pisum sativum L.) was evaluated. Chemical composition of extracts of different plant parts of Typha was also determined. Aqueous (20, 40, 60, 80, and 100 g L−1) and organic extracts (at 0.5, 1, and 2 mg mL−1) were applied to the seeds of two pea cultivars, Douce de Provence and Lincoln, placed in Petri dishes. Application of extracts had a beneficial effect on germination and early seedling growth of both pea cultivars. However, aqueous extract of leaves showed the most beneficial effect at 60 and 40 g L−1 for the cultivars Douce de Provence and Lincoln, respectively. The effect could be attributed to the allelochemicals present in the aqueous extracts. Petroleum ether and chloroform extracts of leaves had the most stimulating effect on the germination and early seedling growth of pea. Analysis of Typha extracts indicated the presence of vitamin E in leaves, which could be responsible forthis stimulation. Moreover, Typha leaves also had substantial amount of flavonoids. In conclusion, the allelopathic activity of of Typha was dependent on the plant part, the solvent nature, the concentration of the extracts tested, and on the pea cultivar. Application of leaf extract was the most effective in improving the germination rate and early seedling growth of pea.

Performance of Pepper Seedlings Developed from Seeds Pretreated with Algal Aqueous Extracts

Abstract This study aims to evaluate the effect of seed priming for two pepper varieties by extracts of two algae thalli on the performance of growth at vegetative stage. The seeds were soaked in thalli aqueous extracts (at 20, 40, 60, 80 and 100 g/L), for 24 h at 28±2°C, rinsed thoroughly with distilled water and then dried to their initial weight as a first batch (SD), a second batch of seeds was considered, corresponding to seeds placed in Petri dishes to germinate directly after washing (SND). Untreated seeds were the control. The results showed than the priming has improved seedlings growth for both varieties. Seed priming with algae aqueous extracts has improved roots and shoots length. The best stimulations were 220% and 70%, respectively, recorded for seedlings of Baklouti and Chargui varieties, following the priming with the extract of Padina pavonica at 40 g/L concentration. These improvements appear to be related to a better photosynthetic intensity, an increase in the number of leaves and the water content, which were noted in plants from pretreated seeds. Finally, the results indicate that, generally, the plantlets from SND were more vigorous. The results of this work show that algae could be an inexhaustible resource of substances, that can be used as an alternative to chemicals used in the pretreatment of seeds, reducing the risk of pollution and preserving the biological material.